Pressure fluid servomotor having



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PRESSURE FLUID SERVOMOTGR HAVING FEEL Filed Nov. l2, 1946 4 Sheets-Sheet l By 'MARQMM 'l April 11, 1950 w. G. LISLE ETAL 2,503,956

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Patented Apr. 11, 1950 PRESSURE FLU'I-lll` SIEIRVOMIYIORl HAVING FEEL MEANS' William. George Lisle; East Bedfont, and Charles Reginald! Ghurni. Tilehurst,l England, assignorsto The` Fairey Aviation Company Limited,

Hayes, England;

Application November 12, 1946, Serial No. 709,240 In Great Britain January-11,1944.

Itis known that; there. are physical limitationsl tor the practical. application. of manually operated control. systems tof aircraft, beyond. which it. be comes? necessary to. utilise some external force. to provide themotive effort.e. g., hydraulic or pneumatic power. In an orthodox hydraulic control'4 system the. manual control is applied to a. valve which. serves tol admit iluid pressure through appropriatepassages to an hydraulic power jack, servo-motor, or the like to obtain movement. in the required sense. Usually, the manual force necessary tofoperate this. valve. is quite small, is reasonablyY constant: throughout all flying condi.- tions, and constitutes the pilots total effort to move thecont-rol surface into any position under circumstances, whereas in a manually operated' flying control system, they pilots effort, at any given; aircraft speed, must increase as deection of the control surface is increased, and ata-ny given'` controlsurface deflection, must inf crease as the speed of the aircraft increases. Hence, a pilot of af manually controlled aircraft becomes accustomed to these force characteristics, by which: he judges his control movements throughout flight,v and any absense of this. socalled.: feel would bev disconcerting and in some circumstances might even be dangerous in manoeuvre.V Another disadvantage of the orthodox arrangement is that if the fluid pressure system beso: damaged as to render it inoperative the pilot isf unable to` control his, aircraft..

Ithas been proposed that a control. column of an; aircraft should be connected with the valve of afluid pressure jack, servo-motor, or the like, bothmembers (piston and cylinder) of which are movable. and that it. should also be connected through lost, motion means with one of said members and. with a surface to be controlled thereby and through a link with the other of said members so that, normally, movement of the control column acts on the fluid pressure valve to bring.' aboutA actuation of the. control surfe-.ceandtc4 a very small, extent on said other movable member, whilst, in the event of failure of; the. fluid pressure system, the. control column will directly;y after predetermined lost motion. on the.- control. surface..

The. object oi'v the presentA invention is tol pro.- vide improved means for actuating control surfaces of an; aircraft.

An advantage to4 be.A derived from the invention is: that they orthodox trimming tab and gear may beeliminatedwith consequent simplification and improved. control characteristics.

To, this end andinYV accordance with the inven- 3' Claims. (Cl. 121-41).

tion the control column of an aircraft is connected with they valve of a. iiuid pressurey jack servo-motor, or the like, both. members of which (e. g. piston and cylinder) are movable and. is also connected, through lostmotion means, with one of said members andy with. the surface to be:- controlled therebyv and, through: a movement. reducing system of levers, of which'. the control col-- umn forms part with the other of saidA members, so that, normally, movement of said control column acts on the fluid pressure, valve to.y bring. about actuation ofthe control surface. and also.- acts to a very small extent on. said other mov able member, Whilst, in the eventI of failure of the fluid pressure system, the'y control column will act directly after predetermined lost. motion, on the control surface.

The movement reducing system of. levers (which maybe made adjustable to: alter the effective leverage to. suit requirements) consists.A ot

the control columnwhich is arranged to function as a lever of the second order, and. one. or more levers of the second order, all said levers being. interconnected so that the work output from. the first lever acts. as the power input to theV second lever, and so on, the leverages being proportionedso thatv the movement necessary for the power input is great as compared with the. movement of the Work output.

One form of the invention is illustrated, by way of example in Figure 1 of the accompanying drawings which is a diagrammatic side view of the control column and a control surface of an aircraft, together with an hydraulic servo-motor and its valve arrangements; Figure 2 is an enlarged, partly diagrammatic, sectional elevation of an optional valve control; Figure 3 is an enlarged sectional view of the hydraulic jack and its valve arrangements.; and. Figures 4 and 5 are enlarged diagrammaticviews illustrating two diiferentiiuid connections established` by the optional valvecontrol of Figure. 2.

Asshown in Figures-1 and 3both the cylinder av.' and the piston b. of an hydraulic. servo-motorr by which a control surface c of an aircraft is tobe. actuated. are movable. The control column d1 of the aircraft is pivoted, at its lower end, at e, to. a fixed. part of the aircraft. At points; in.. termediate of its length, it is. connected directlyv with the valve gv (shown generally as g Figure 1lof the hydraulic servo-motor ab and through a pin h. and slot i. connectionwith a link 7c one end of which is. attached rigidly to the. cylinder. a of the hydraulic servo-motor and the other end of. which. is. pivotally attached. to an= arm m pro.- 

